Environment-friendly convert from waste textile sludge into lightweight aggregates by non-sintered technology: physical properties and mechanism

It is of utmost importance to mitigate environmental pollution by employing clean and environmentally friendly technology for the treatment of textile sludge. This paper focuses on utilizing textile sludge as the primary raw material in the production of lightweight aggregates for the construction industry, using a non-sintered method that is more eco-friendly compared to traditional sintering technology. The optimal raw material ratio and process parameters for fabricating non-sintered lightweight aggregates are determined as follows: a sludge/cement ratio of 2.25, fly ash addition of 5%, additive addition of 1%, and curing time of 28 days. These parameters result in physical properties including a compressive strength of 6.93 MPa, bulk density of 753 kg/m³, and 1h water absorption rate of 17.98%. The hydration mechanisms have been investigated through X-ray diffraction and scanning electron microscopy, revealing that C–S–H gel and Ettringite produced by the hydration reaction significantly contribute to the physical properties. Furthermore, it has been observed that Zn²⁺ present in the textile sludge reacts within the hydration system, ultimately transforming into insoluble Ca(Zn(OH)₃)₂·2H₂O and Zn(OH)₃⁻. These compounds are captured by C–S–H gel, effectively eliminating potential risks associated with heavy metal Zn during the resource utilization process of textile sludge. In summary, the innovative method proposed in this paper could effectively achieve the resourceful and harmless utilization of textile sludge.